Thread controlling device for sewing machines



J. R. NUNN THREAD CONTROLLING DEVICE FOR SEWIVNG MACHINES Filed Sept. 20, 1938 l y gime/wm clceyoh R. Nunn www,

wi-ruw# Patented Dec. 26, 1939 UNITED STATES THREAD CONTROLLING DEVICE FOR SEWING MACHINES Joseph R. Nunn, Brooklyn, N. Y., assigner to The Singer Manufacturing Company, Elizabeth, N. J., a corporation of New Jersey Application September 20, 1938, Serial No. 230,758

1 Claim.

This invention relates to needle-thread controlling mechanisms for lock-stitch sewing machines and has for its object to provide means for conveniently changing the effective stitch- 5 setting action of a conventional needle-thread handling mechanism, thereby to increase the work-range of the sewing machine.

For certain kinds of work involving the stitching of leather and like materials, it is desirable to draw both of the interlocked threads of a lock-stitch seam well into the material, whereby the stitches present the same appearance upon opposite faces of the work. To accomplish this object, it has heretofore been the practice when stitching leather of firm texture to provide a conventional needle-thread handling mechanism with a take-up lever proportioned to effectively set the stitches. However, softer and weaker leather tends to tear under the conditions requisite to properly set stitches in leather of rmer texture. Consequently, the same sewing machine was unadapted to meet the conditions incidental to the prevalent practice of frequently changing the kind of leather materials to be stitched.

'Ihe present invention consists in the combination with a conventional needle-thread takeup lever of a sewing machine, of a device providing for conveniently regulating the iinal setting of stitches, as hereinafter described and disclosed in the accompanying drawing which illustrates a preferred embodiment of the invention and in which:

F'ig. l is a front side elevation, partly in section, of a portion of a lock-stitch sewing machine i containing the present improvement. Fig. 2 represents, in perspective, separate views oflthe parts of the stitch-setting regulating device shown detached from the sewing machine.

The sewing machine which is in part illus- 40 trated in the drawing corresponds substantially to that more fully disclosed in the United States patent to J. A. Knox, No. 1,864,136, June 2l, 1932, said sewing machine having a work-support I including a throat-plate 2. Overhanging the work-support is a hollow bracket-arm 3 which terminates in a head 4.

suitably journaled in the bracket-arm 3is a rotary actuating shaft 5 carrying at one end a crank-disk 6, connected by a link I to a needle-bar 8. The needle-bar 8 carries an eyepointed needle 9 and is journaled for endwise reciprocation in vertically alined bearings provided in a swinging frame I0. The frame I0 is hung upon a fulcrum-pin suitably fixed in the bracket-arm head '4 so that the pivotal axis of.4 the frame Il) is substantially parallel with the axis of rotation of the actuating shaft 5.` The frame I0 derives vibratory movements from the usual crank-arm I2 on one end of a needlefeed rock-shaft. I3, journaled in the bracket-arm 6 3 and actuated in the usual or in any suitable manner. Cooperating with the needle 9 below the worksupport, in the formation of lock-stitches, is a rotary hook I4 of the vertical-axis 'type and 10 having a needle-thread-loop seizing beak |47. Journaled in the rotary hook I4 is the threadcase I5 restrained, in the usual or any suitable manner, against rotation with the hook I4. The rotary hook I4 is carried by the upper end of a 15 vertically disposed hook-shaft |25` rotatably journaled in a hook-saddle I'l, said hook-shaft I5 carrying a bevel-gear I8 driven by a bevel-gear I9 upon one end of a horizontally disposedr hookactuating shaft 20 also journaled in the hook- .20 saddle The'hook-actuating shaft 20 is actuated in the usual or any suitable manner and in the present case rotates once for each rotation of the shaft 5, the bevel-gears I8 and I9 being proportioned so that .the hook-shaft I6 25 rotates twice for each rotation of its actuating shaft 20. The work is advanced by a horizontal-axis feed-wheel 2| which partly extends above the work-support through aslot in the throat-plate 30 2, said feed-wheel being disposed directly adjacent the rotary hook |4 and being actuated in the conventional manner to continuously` ad- Vance the work. Opposed to the feed-wheel. 2| is a presser-roller 22 carried by a presser-bracket 35 -23 secured to the .lower end of the usual springdepressed presser-bar 24 Qwhich is endwise vertically movable in the bracket-arm head 4.

From its supply (not shown), the needlethread N is ypassed through a suitably aperturedI 40 thread-guide 25, upon the bracket-arm head 4, and then between the disks of the usual tensiondevice 26 into engagement with the conventional The arm 3l of the take-up lever is slidingly embraced by a sleeve 32 pivotally carried by the upper end of the needle-bar link 1, and the arm 28 of the take-up .lever extends forwardly through a slot 33 in the head 4.

In Fig. 1 of the drawing, the arm 2B is illustrated as substantially at the lower end of its path of movement, i. e., the arm 28 has completed its slack-thread giving movement and is about to begin to pull upwardly upon the thread to draw it off the rotary hook and to set the stitch. It will be noted from Fig. 1 of the drawing, that the arm 28 in its lowest position is nevertheless above the level of the tension device 26 and its slack-thread controller spring 2'5, so that in moving upwardly to pull up the needlethread loop and to set the stitch, the thread N acts to pull the controller-spring 21 upwardly, said spring functioning primarily to take up the slack thread initially given by the take-up arm 28 as it commences its downward movement, as is well understood in the art.

In accordance with the present invention, there is provided a regulating device for controlling the quantity of slack thread given up by the takeup arm as it approaches the limit of its slackgiving movement, whereby the final setting of the stitches will be effected by the rotary hook in its expansion of the needle-thread loop to cast it about the thread-case I5, as will be understood from the following description.

Secured by screws 34 upon the front face oi the bracket-arm head 4, adjacent the take-up arm 28 and between the thread-guide 25 and the tension-device 2t, is a supporting plate 55 provided with a thread-confining loop 36, said loop 35 functioning primarily to restrain the needlethread N from excessive whipping on the needle side of said take-up lever 28.

Adjustably pivoted upon the supporting-plate 35, by a screw 31 threaded into an aperture 38 in said plate 35, is a carrier-plate 3S provided with an aperture 49 to receive the pivot-screw Si'. The carrier-plate 39 is provided with an arcuate slot 4I having the pivot-screw 3T as its cen-- ter of curvature, through which slot passes a securing screw 42 threaded into an aperture 153 in the supporting plate 35. An edge of the carrierplate 39 is shaped to provide a pointer 44 which overlies suitable graduations provided upon the supporting plate 35, thereby to indicate adjusted Heye of the take-up lever 28 to the needle.

in the carrier-plate to provide for conveniently passing the thread N into the loop 45. The thread-guiding loop 45 is illustrated in full lines in Fig. 1 of the drawing at one extreme of adjustment of the carrier-plate and is illustrated in dotted lines in its opposite extreme position.

It will be noted that the needle-thread N passes from the slack-controller spring 2'! through the adjustable guide-loop d5 and then through the When the carrier-plate 3S is disposed in the position thereof illustrated by full lines in Fig. 1, the take-up lever 28 in its descending slack-giving movement bends the thread N sharply about the guide-loop 45, whereby the take-up lever 28 gives up a minimum of thread for expansion by the rotary hook id. Consequently, the expansion of the needle-thread loop by the rotary hook increases the tension of the thread sufficiently to cause the loop-limb leading to the previously formed stitch to act to further and finally set said stitch.

However, when stitching softer materials, it is not only unnecessary to impose the same pull upon the needle-thread to set stitches into the work, as is required in materials of rmer texture, but when stitching materials such as soft leather and leather imitations there is a liability that excessive thread tension will cause the work material to tear between stitches.

The present invention provides for the above noted contingency. By adjustment of the guideloop i5 into the position thereof illustrated by dotted lines in Fig. l of the drawing, the thread is not bent about said gude-loopby the take-up lever in its slack-thread giving movement and consequently the guide-loop is rendered ineffective to modify the length of thread given up by said lever. Under the circumstances, the thread is not tensioned to the extent before described, by the expansion of the thread-loop by the looptaker and the stitch is set by the thread drawing up action alone of the take-up lever. It will be understood, of course, that the setting of the stitches can be further controlled by adjustment of the guide-loop d5 into positions intermediate its limits of adjustment.

Having thus set forth the nature of the invention what I claim herein is:

In a sewing machine, in combination with a reciprocatory needle, a loop-taker complemental to said needle in the formation of lock-stitches, a needle-thread tensioning device, and a vibratory take-up lever, of a stationary thread-guide disposed adjacent said take-up lever in position to modify the length of thread given up by said lever, and means providing for adjustment of said thread-guide into an ineffective position thereof.

JOSEPH R. NUNN. 

